wcaseyharman
Electrical
- Oct 31, 2022
- 299
Hi,
We had event on one of our thermal generating units where it appears an SCR went into lockup (latchup). The equipment is a 1982 vintage GE 7E gas turbine (74MW) with a GE 7A4 generator (13.8kV, 94MVA). The bridge is an original GE busfed half-controlled bridge with a Basler DECS400 front end upgrade applied in 2010. PPT secondary is 480V.
The event occurred several seconds after a transmission fault on the 115kV system about 30 miles away. The unit responded to the event, but the bridge appeared to get stuck - the control command went to full negative (-10V, minimum field voltage) but the field voltage stopped at 325V for 10 seconds. The field current rose accordingly and the unit tripped off on generator overvoltage. I calculated the field voltage for a 1 SCR lockup would be and I get 324V.
Has anyone else encountered SCR lockup? If so, what caused it and how did you fix it?
Thanks in advance!
We had event on one of our thermal generating units where it appears an SCR went into lockup (latchup). The equipment is a 1982 vintage GE 7E gas turbine (74MW) with a GE 7A4 generator (13.8kV, 94MVA). The bridge is an original GE busfed half-controlled bridge with a Basler DECS400 front end upgrade applied in 2010. PPT secondary is 480V.
The event occurred several seconds after a transmission fault on the 115kV system about 30 miles away. The unit responded to the event, but the bridge appeared to get stuck - the control command went to full negative (-10V, minimum field voltage) but the field voltage stopped at 325V for 10 seconds. The field current rose accordingly and the unit tripped off on generator overvoltage. I calculated the field voltage for a 1 SCR lockup would be and I get 324V.
Has anyone else encountered SCR lockup? If so, what caused it and how did you fix it?
Thanks in advance!